安装完win7与ubuntu，突然发现不知如何启动win7。

zzzmmmnnn@zzzmmmnnn-TWJ:~$ sudo update-grub
Generating grub configuration file ...
Warning: Setting GRUB_TIMEOUT to a non-zero value when GRUB_HIDDEN_TIMEOUT is set is no longer supported.
Found linux image: /boot/vmlinuz-3.16.0-4-generic
Found initrd image: /boot/initrd.img-3.16.0-4-generic
Found linux image: /boot/vmlinuz-3.15.0-6-generic
Found initrd image: /boot/initrd.img-3.15.0-6-generic
Found memtest86+ image: /memtest86+.elf
Found memtest86+ image: /memtest86+.bin
Found Windows 7 (loader) on /dev/sda1
done

怎么安装啊，

安装双系统求指导！